CN1674334A

CN1674334A - Fuel cell system and stack used thereto

Info

Publication number: CN1674334A
Application number: CNA2005100592749A
Authority: CN
Inventors: 李东勋; 权镐真; 安圣镇; 金亨俊; 徐晙源; 金宗满; 尹海权; 殷莹讃
Original assignee: Samsung SDI Co Ltd
Current assignee: Samsung SDI Co Ltd
Priority date: 2004-03-25
Filing date: 2005-03-25
Publication date: 2005-09-28
Anticipated expiration: 2025-03-25
Also published as: CN1330028C; KR100529080B1; US7329472B2; JP2005276811A; US20050214625A1; KR20050095157A

Abstract

Disclosed is a fuel cell system wherein the flow of fuel and oxygen is optimized thereby improving the thermal efficiency of the entire system. The fuel cell system comprises at least one stack for generating electrical energy by an electrochemical reaction between hydrogen gas and oxygen, a fuel supply portion for supplying fuel to the stack, and an oxygen supply portion for supplying oxygen to the stack. The stack is formed in a stacked configuration with MEAs and separators. The separators are positioned on either surface of the MEAs. The separators have a plurality of ribs proximate to the MEAs which define a plurality of channels wherein the ratio of a width of the channels to the width of the ribs is from about 0.8 to 1.5.

Description

Fuel cell system and used folding thereof

Technical field

The present invention relates to a kind of fuel cell system and used folded (stack) thereof, relate more specifically to a kind of fuel cell system and folded, be used for optimizing the size that is formed on the passage between dividing plate (separator) (for example bipolar plates) and the septum electrode assembly (membrane electrode assembly) (being hereinafter referred to as MEA).

Background technology

Fuel cell is a kind of system that is used to produce electric energy.In fuel cell, oxidant and the chemical reaction that is included between the hydrogen in the hydrocarbon family material (for example methyl alcohol, natural gas) can be converted into electric energy.This fuel cell is characterised in that as the electric energy of the accessory substance of the electrochemical reaction that takes place under the situation of not having burning and the generation of heat energy.

According to the electrolytical type of using in the fuel cell, fuel cell can be divided into the fuel cell of number of different types, for example, phosphate fuel cell, molten carbonate fuel cell, Solid Oxide Fuel Cell and polymer dielectric or alkaline fuel cell.Although each in these dissimilar fuel cells is used identical principle work, they are different on used fuel, catalyst and electrolytical type and actuation temperature.

Recently developed polymer electrolyte membrance fuel cells (PEMFC).Compare with other fuel cell, PEMFC has outstanding output characteristic, low working temperature and starts fast and response characteristic.PEMFC can be used in vehicle, family and the building, and is used for the power supply of electronic installation.Therefore, PEMFC has very wide range of application.

The basic element of character of PEMFC is folded, fuel tank and petrolift.The folded main body that forms fuel cell.The fuel supply that petrolift will be stored in the fuel tank is extremely folded.Can also use reformer (reformer) fuel reforming, thereby form pure relatively hydrogen and hydrogen is supplied to folded.

In PEMFC, thereby the operation petrolift will be delivered to reformer from the fuel of fuel tank.Fuel is reformed in reformer, thereby produces hydrogen, thereby hydrogen produces electric energy with oxygen generation chemical reaction in folded.

It is folded to use the fuel cell of direct type methanol fuel cell (below be called " DMFC ") that hydrogeneous liquid methanol fuel directly is supplied to, and therefore can not comprise reformer.Lacking of reformer is difference between PEMFC and the DMFC.

Fig. 8 is a folded partial section used in the fuel cell system according to prior art, and wherein MEA and dividing plate fit together.

With reference to Fig. 8, some embodiment of fuel cell can comprise and are used for fully producing the folded of electricity.Fold and to constitute by the structure of stacked element cell.Stacked element cell can comprise the plurality of units battery with MEA51 and dividing plate 53, or ten or more a plurality of element cell.

MEA51 has electrolyte membrance and is installed in anode electrode and cathode electrode on its two opposite surfaces.Dividing plate 53 has passage 55,57, and hydrogen that the oxidation/reduction reaction of MEA51 is required and/or air are supplied to anode electrode and cathode electrode through this passage.

That is, through the passage 55 and 57 of dividing plate 53, hydrogen is supplied to anode electrode respectively, and air is supplied to cathode electrode.In this process, hydrogen is in the anode electrode oxidation, and oxygen reduces at cathode electrode.The electron stream that produces in this operating period produces electric current.In addition, water and heat have been produced by electrochemical reaction.

More specifically, each dividing plate 53 comprises a plurality of ribs 59 of the neighbouring surface of being close to MEA, and it defines the passage 55,57 that is used to supply with required hydrogen and air.In fact, passage places between each rib 59.

Usually, be arranged at dividing plate under the situation of MEA51 both sides, the passage 55,57 that is used for supplying with respectively required hydrogen and air is orthogonal.Thus, in sectional view shown in Figure 8, show the single passage 55 that is used for hydrogen supply, show simultaneously and be used for air fed a plurality of passage 57.

In above-mentioned fuel cell system, folded structure should strengthen the diffusion in folding, and keeps the pressure of fuel between diffusion period simultaneously, thereby improves the efficient of fuel cell.Herein, an essential condition that is used to design stack structure is the size of passage 55,57.That is, in dividing plate 53, the size of passage has played important function for active region diffusion hydrogen and the air from MEA51 to its diffusion layer and for the contact resistance of controlling the electric current that produces among the MEA51.

Summary of the invention

In one aspect of the invention, provide a kind of fuel cell system, the ratio of width and the width of rib that it has optimized the groove of the passage that is formed for fueling and air has improved the fuel diffusion performance thus and has reduced pressure wherein and fallen.

In an exemplary embodiment of the present invention, a kind of fuel cell system comprises: at least one is folded, is used for producing electric energy by the electrochemical reaction between hydrogen and the oxygen; The part of the fuel supply is used for to folded fueling; And the oxygen supply part, be used for to the folded oxygen of supplying with.The folded stacked structure that has by the separated a plurality of MEA of dividing plate that is formed.Dividing plate has rib, and this rib closely contacts with contiguous MEA, and forms oxygen and hydrogen and flow through wherein groove.The ratio of the width of groove and the width of corresponding rib is between about 0.8 and about 1.5.

Groove is supplied with hydrogen and the extremely folded passage of oxygen with acting on.Be used to supply with the side of the passage operated by rotary motion of hydrogen at the close anode electrode of dividing plate.The passage that is used to supply with oxygen is arranged on the opposite side of the close cathode electrode of each dividing plate.Supply with the passage of hydrogen general with the passage quadrature of supplying with oxygen.

In an embodiment of the present invention, the active region of MEA is lower than 40cm ², the width of groove is in from about 0.8mm to the scope of about 1.4mm.Rib is constructed to from dividing plate outstanding, and groove is constructed in the recessed dividing plate.

Description of drawings

Fig. 1 is the schematic diagram of the fuel cell system of one exemplary embodiment according to the present invention;

Fig. 2 is the folded decomposition diagram of Fig. 1;

Fig. 3 is the decomposition diagram of the folded element cell of pie graph 1;

Fig. 4 is the folded partial section of Fig. 1, and wherein MEA and dividing plate fit together;

Fig. 5 is the exploded partial cross-sectional view of the dividing plate of Fig. 1;

Fig. 6 is a curve chart, and the relation of the width of the groove that forms hydrogen channel and air duct and relative power density (below be called " RPD ") is shown;

Fig. 7 is a curve chart, and the width of the rib that forms hydrogen channel and air duct and the relation of RPD are shown; And

Fig. 8 is a used folded partial section in the conventional fuel cell system, and wherein MEA and dividing plate fit together.

Embodiment

Introduce exemplary embodiment of the present invention in detail now with reference to accompanying drawing.

Fig. 1 is the schematic diagram of the fuel cell system of one exemplary embodiment according to the present invention; Fig. 2 is the folded decomposition diagram of Fig. 1.

See figures.1.and.2, in an embodiment of the present invention, fuel cell system can comprise the part of the fuel supply 1 that is used for to reformer 3 fuelings.The hydrogen that is produced by the fuel of being supplied with in the reformer 3 can offer folded 7.In addition, oxygen is supplied with part 5 to folded 7 air supplies.In folded 7, hydrogen can be converted into electric energy with the chemical reaction that contains aerial oxygen, produces electric current thus.

Fuel supply assembly 1 comprises fuel tank 9 and pump 11.Fuel can be stored in the fuel tank 9.The fuel that uses among some embodiment can be liquid fuel, for example methyl alcohol or ethanol, and perhaps fuel can be the gaseous fuel such as natural gas.In this embodiment, pump 11 is produced liquid fuel for the reformer 3 that wherein produces hydrogen.Then, hydrogen flows in folded 7.

In an embodiment of fuel cell system, hydrogeneous liquid fuel can directly be supplied to folded 7 as in the DMFC system.Below, suppose that this fuel cell system applications is in the PEMFC type.

As shown in Figure 3, air supply part 5 comprises the air pump 13 that is used to folded 7 production air.In folded 7, the air air duct 17 of flowing through.The hydrogen channel 15 of hydrogen in folded 7 flows.

As shown in Figure 1, hydrogen is through the part of the fuel supply 1 and be supplied to folded 7 by reformer 3.Air is supplied with part 5 through air and is supplied to folded 7.Electric energy produces by hydrogen and the electrochemical reaction that is present between the oxygen in the extraneous air.In addition, heat and water have been produced.

Fig. 3 shows has the folded 7 of at least one element cell 19, and it is used for the oxidation/reduction reaction generation electric energy of the oxygen that comprises by the hydrogen that produced by reformer 3 and air.Each element cell 19 is by placing septum electrode assembly (MEA) 21 on the minimum unit battery that is formed for producing electric current between two dividing plates 23,25.Fig. 2 shows folded 7 a plurality of such element cell 19 that is combined into embodiment with stromatolithic structure.End plate 27 is installed on the relative outermost layer of a plurality of element cells 19.End plate 27 can be the alternating structure of dividing plate 23,25.A plurality of element cells 19 by means of pass its outermost layer and with combine with the fixing set bolt 19a of nut 19b, thereby form folded 7 of stromatolithic structure.

Fig. 3 is the decomposition diagram of the folded element cell of pie graph 1.Fig. 4 is the folded partial section of Fig. 1, and wherein MEA and dividing plate are assembled together.

With reference to Fig. 3 and 4, each dividing

plate

23,25 is provided with near the surface of MEA21, thereby forms hydrogen channel 15 and air duct 17 between the surface of dividing

plate

23,25 and MEA21.The anode electrode 29 of hydrogen channel 15 contiguous MEA21.Air duct 17 is near the cathode electrode 31 of MEA21.Herein, hydrogen channel 15 and air duct 17 can be pressed the parallel strip configuration and arrange on main body 23a, the 25a of dividing

plate

23,25, and hydrogen channel 15 and air duct 17 are provided so that usually passage is orthogonal.Yet in other embodiments, hydrogen channel 15 and air duct 17 can be arranged by other configuration.

And for example shown in Fig. 2 to 4, when dividing

plate

23,25 closely during contact MEA21 surperficial, hydrogen channel 15 vertical arrangements.The surface and the air duct 17 between the dividing plate 25 that are formed on MEA21 are transversely arranged, make air duct 17 and hydrogen channel 15 quadratures.

MEA21 places between a pair of dividing

plate

23,25, and it comprises the active region 21a (shown in Fig. 2) with preliminary dimension, and oxidation/reduction reaction takes place in this active region.Anode electrode 29 and cathode electrode 31 can be arranged on the both side surface of active region 21a, or are inserted with electrolyte membrance 33 between two

electrodes

29,31.

More specifically, hydrogen through being formed on MEA21 anode electrode 29 and the hydrogen channel 15 between the dividing plate 23 be supplied to anode electrode 29.Thereby hydrogen is supplied to gas diffusion layers to spread towards catalyst layer.Catalyst layer has promoted the oxidation reaction of hydrogen, and the electronics of conversion is outwards attracted, feasible mobile generation electric current by electronics.Hydrogen ion moves to cathode electrode 31 through electrolyte membrance 33.

In addition, closely the cathode electrode 31 of the MEA21 of contact and the oxygen passage 17 between the dividing plate 25 are supplied to cathode electrode 31 through being formed on each other to contain aerial oxygen.As hydrogen, thereby oxygen supply spreads to gas diffusion layers towards catalyst layer.Thereby catalyst layer has promoted the conversion reaction of hydrogen ion, electronics and oxygen to produce electricity and water.

In addition, electrolyte membrance 33 is formed by solid polymer electrolyte, and has the degree of depth of 50 to 200 μ m.The hydrogen ion that produces in the catalyst layer of anode electrode 29 moves through the oxonium ion that electrolyte membrance 33 produces in the catalyst layer of cathode electrode 31.The ion-exchange of gained produces water.

Fig. 5 is the exploded partial cross-sectional view of dividing plate shown in Figure 1.Because similar each other on dividing

plate

23,25 structures, Fig. 5 shows a dividing plate 23, however following introduction can illustrate dividing

plate

23,25 both.

With reference to Fig. 5, dividing

plate

23,25 comprises the hydrogen that a plurality of oxidation/reduction reactions that are used to supply with

electrode

29,31 places that occur in MEA are required and the passage of air.As mentioned above, these passages can be hydrogen channel 15 or oxygen passage 17.Hydrogen channel 15 and oxygen passage 17 each dividing

plate

23,25 each with two surfaces of MEA21 in a formation (as shown in Figure 4) when closely contact.Hydrogen channel 15 is provided with near the anode electrode 29 of MEA21.Air duct 17 is provided with near the cathode electrode 31 of MEA21.Limit groove 23c, 25c from side-prominent rib 23b, the 25b of main body 23a, the 25a of dividing plate 23,25.In one embodiment, when dividing

plate

23,25 was provided with near MEA21, groove 23c, 25c can be used as hydrogen channel 15 or air duct 17.

This structure allows groove 23c, the size automatic setting rib 23b of 25c, the size of 25b, has wherein set the surface area of the active region 21a of MEA21.In one embodiment, the sectional area of rib 23b, 25b and groove 23c, 25c (sectional area of vertical line intercepting along the longitudinal direction) can be approximated to be square.Yet the geometry that can use other is as sectional area.

The groove 23c that forms hydrogen channel 15 is connected with reformer 3, and the groove 25c that forms air duct 17 is connected with air pump 13.Therefore, the hydrogen-rich gas that produces in the reformer 3 and the air of pump 13 pumpings are supplied to end plate 27 through hydrogen channel 15 and air duct 17.In the embodiment shown in fig. 4, hydrogen-rich gas is supplied to the end plate of the relative both sides of element cell with air, thereby allows hydrogen-rich gas and air to flow on the contrary.Any remaining hydrogen and air are discharged at another end plate 27 places.

The width W c of the width W r of rib 23b, 25b and groove 23c, 25c can influence the flow through speed of

passage

15,17 of hydrogen and air.Therefore, section A will be determined by the width W c and the height H c of the

passage

15,17 that forms groove 23c, 25c.As the width W c of the width W r of rib 23b, 25b or groove 23c, 25c not fixedly the time, can use mean value.

For improving the efficient of fuel cell, the contact resistance of electric current present remained in the scope that can allow during expectation was folded.Hydrogen or oxygen diffusion performance that also expectation, the gas diffusion layers of MEA21 have raising descend with the folded middle pressure that reduces.For realizing these targets, suitably control channel 15,17-are the groove 23c of dividing

plate

23,25, the section A of 25c-.In this embodiment, optimize the width W r of rib 23b, 25b and the ratio of the width W c of groove 23c, 25c, thereby realize these purposes.

Be supplied to folded energy for the diffusion that strengthens hydrogen and air with it, use relative power density (below be called " RPD ") to come the performance of test fuel cell.Calculate RPD by the performance number that subduction in the performance number that produces from folded 7 consumes in folded 7, the difference of gained is divided by the gross area of active region 21a then.Such RPD value is shown in the table 1,2.Table 1 shows the relation of width W c and the RPD of groove 23c, 25c.

Table 1

Well width (mm)	????0.5	????0.8	????1	????1.2
Well width (mm)	????0.5	????0.8	????1	????1.2	??RPD(mW/cm ²)	????142	????248	????254	????259

After hydrogen is supplied to anode electrode 29 and oxygen and is supplied to cathode electrode 31, when the width W c of groove 23c, 25c is changed under non-heating status, calculate RPD.The result is shown in Figure 6.

Fig. 6 is a curve chart, and the width of the groove that forms hydrogen channel and air duct and the relation of RPD are shown.

With reference to Fig. 6, fuel battery performance improves when the width W c of groove 23c, 25c is bigger, allows to improve the diffusion of hydrogen and oxygen.Yet groove 23c, 25c arrange near the active region with predetermined area, make that the width W r of rib 23b, 25b reduces if the width of groove 23c, 25c surpasses preset width.Be lower than preset width if the width W r of rib 23b, 25b is reduced to, then the contact resistance of electric current present increases among the MEA21.Therefore, note, the width W c by widening groove 23c, 25c and the width W r that makes rib 23b, 25b narrow to be lower than preset width improve fuel cell performance aspect, have restriction.

In experimental test, determined at the active region of MEA21 21a less than 40cm ²The time, the optimization width W c of groove 23c, 25c at about 0.8mm to the scope of about 1.4mm.

Table 2 shows the ratio of width W r of the width W c of groove 23c, 25c and rib 23b, 25b and the relation of RPD.

Table 2

Ratio (Wc/Wr)	????0.5	????1	????1.2	????1.5
Ratio (Wc/Wr)	????0.5	????1	????1.2	????1.5	?RPD(mW/cm ²)	????172	????255	????252	????265

After hydrogen is supplied to anode electrode 29 and oxygen and is supplied to cathode electrode 31, when the ratio of the width W r of the width W c of groove 23c, 25c and rib 23b, 25b is changed under non-heating status, calculate RPD.The result is shown in Figure 7.Fig. 7 is a curve chart, and the width of the rib that forms hydrogen channel and air duct and the relation of RPD are shown.

With reference to Fig. 7 as seen, from about 0.8 to about 1.5 scope the time, RPD is preferred at the ratio Wc/Wr of the width W r of the width W c of groove 23c, 25c and rib 23b, 25b.In one embodiment, preferably, ratio Wc/Wr about 0.8 to about 1 scope.Perhaps, in some embodiments, about 1.2 ratio Wc/Wr to about 1.5 the scope are desired.

More specifically, if ratio Wc/Wr is lower than 0.8, then since the joint face of the active region 21a of MEA contact gas diffusion layers reduce, so RPD reduces.Increase by index law ground for the contact resistance (factor that reduces of RPD) of contact-making surface hydrogen and the advancing the speed of air velocity (the increase factor of RPD) with respect to the contact-making surface of flowing through, the summation of RPD reduces thus.In addition, if increase through the hydrogen and the air velocity (the increase factor of RPD) of contact-making surface, then the internal pressure that occurs among groove 23c, the 25c reduces.

On the other hand, if ratio Wc/Wr is about 1.5 to about 1.8 scope, then RPD reduces.Although the joint face of the active region 21a of MEA contact gas diffusion layers increases, reduce through the hydrogen of contact-making surface and the speed and the contact resistance of air.Thus, the width W c by widening groove 23c, 25c and the width W r that makes rib 23b narrow down improve fuel cell performance aspect, have limit.

Therefore, in 0.8 to 1.5 scope, then the value of RPD is preferred as if ratio Wc/Wr.Its reason is that the width W r of rib 23b, 25b is increased, thereby has reduced contact resistance; The speed of hydrogen and air is increased, thereby has increased diffusion velocity.

Although below describe embodiments of the invention in conjunction with the specific embodiments in detail, it should be understood that, the invention is not restricted to the disclosed embodiments, on the contrary, should contain the various changes and/or the equivalent arrangements that comprise in the spirit and scope of the invention that claims limit.

As mentioned above, above-mentioned fuel cell system has a structure, and it makes the slot part of the dividing plate that closely contacts with MEA can optimize with the width ratio of flank, thus the raising of the heat efficiency of whole system.

In addition, fuel cell system of the present invention has a structure, and it makes that wherein contact resistance of electric current present can remain in the preset range, thereby improves the fuel diffusion performance and the pressure that reduces wherein falls.

Claims

1. fuel cell system comprises:

At least one is folded, is used for producing electric energy by the electrochemical reaction between hydrogen and the oxygen;

The part of the fuel supply is used for to described folded fueling; And

The oxygen supply part is used for to described folded supply oxygen,

Wherein, a plurality of septum electrode assemblies and dividing plate are drawn together in described stacked package, dividing plate is arranged on two surfaces of each septum electrode assembly, described dividing plate has a plurality of ribs that closely contact with described septum electrode assembly, described rib limits groove, and the width of wherein said groove is 0.8 to 1.5 with the ratio of the width of described rib.

2. fuel cell system as claimed in claim 1, wherein said groove is with acting on the passage of supplying with hydrogen and oxygen.

3. fuel cell system as claimed in claim 2, the passage of wherein supplying with hydrogen is arranged on a side of the close anode electrode of described dividing plate; The passage of supplying with oxygen is arranged on the opposite side of the close cathode electrode of described dividing plate.

4. fuel cell system as claimed in claim 2 is wherein supplied with the passage of hydrogen and the passage quadrature of supply oxygen.

5. fuel cell system as claimed in claim 1, wherein each septum electrode assembly has less than 40cm ²The active region, and the width of described groove is 0.8 to 1.4mm.

6. fuel cell system as claimed in claim 1, wherein said rib are constructed to from described dividing plate outstanding, and described groove is constructed in the recessed described dividing plate.

7. fold for one kind, comprising:

The septum electrode assembly is used to promote the oxidation/reduction reaction between hydrogen and the oxygen; And

Dividing plate is used for to described septum electrode assembly hydrogen supply and oxygen,

Wherein, described dividing plate comprises a plurality of ribs that closely contact and limit a plurality of grooves with described septum electrode assembly, and the width of wherein said groove is 0.8 to 1.5 with the ratio of the width of described rib.

8. as claimed in claim 7 folded, wherein said groove is with acting on the passage of supplying with hydrogen and oxygen.

9. as claimed in claim 8 folded, the passage that wherein is used to supply with hydrogen is arranged on a side of close the anode electrode of each dividing plate, and the passage of supply oxygen is arranged on the opposite side of the close cathode electrode of each dividing plate.

10. as claimed in claim 8 folded, as wherein to be used to supply with the passage of hydrogen and to be used to supply with oxygen passage quadrature.

11. as claimed in claim 7 folded, wherein each septum electrode assembly has less than 40cm ²The active region, the width of described groove is 0.8 to 1.4mm.

12. as claimed in claim 7 folded, wherein said rib is constructed to from described dividing plate outstanding, described groove is constructed in the recessed described dividing plate.